Assessment of the Effects of Intermittent Mixing On Solid-State Fermentation for Biomass-Degrading Enzymes Production by Different Fungal Strains

Abstract

The use of solid-state fermentation (SSF) for the production of industrial enzymes has received increasing attention over the years. However, the implementation of large-scale SSF processes requires an understanding of the effects of mixing on microorganism growth and product formation. This paper describes a systematic comparison of the effects of intermittent mixing on SSF, in terms of the production of biomass-degrading enzymes (endoglucanase, β-glucosidase, and xylanase) by different fungal strains (Aspergillus niger, Aspergillus oryzae, and Trichoderma reesei). It was found that when A. niger was cultivated using wheat bran as the sole substrate, mixing had a negative effect on the production of enzymes. However, this effect was minimized when the cultivation was carried out using a combination of wheat bran and sugarcane bagasse (3:1 on a dry mass basis) as substrate. In addition, use of the combined substrate enabled improvement of the overall enzymatic production by A. niger. Considering all the fungi tested, the enzyme most negatively affected by mixing was -glucosidase. It is therefore important that special attention be given to -glucosidase during bioprocess development for biomass-degrading enzymes production under SSF in large-scale bioreactors. These findings can contribute to selection of the most appropriate cultivation conditions for implementation of large-scale SSF processes.